Cell Theory PDF

Cell Theory Unit 2 Lesson 1 Cell Theory Students will be able to: Describe the principles that make up Cell Theory Outline the history of the Cell Theory. Key Vocabulary: Animalcules, cell, cellular reproduction, cell theory, daughter...

Cell Theory Unit 2 Lesson 1 Cell Theory Students will be able to: Describe the principles that make up Cell Theory Outline the history of the Cell Theory. Key Vocabulary: Animalcules, cell, cellular reproduction, cell theory, daughter cell, heredity information, spontaneous generation Cell Theory The cell theory is one of the key principles that underpins all of Biology. It is now universally accepted that all living organisms are made up of one or more cells, and that these are the most basic structure all living organisms. Cell Theory Today, cell theory has six core principles. 1. All living organisms are made up of cells. 2. The cell is the basic unit of life. 3. A new cell comes from a pre-existing cell. 4. All hereditary information is passed from a parent cell to a daughter cell during cellular reproduction. 5. All cells have similar chemical composition. 6. Energy flow occurs within cells. Cell Theory Comprehension Check For each of the following statements decide which of the 6 core principles of cell theory it describes. 1. All living things have the same functional unit. 2. Cell division produces more cells of the same kind. 3. The DNA in a daughter cell will be the same as that found in the parent cell 4. Cells have metabolic processes. 5. The four main macromolecules are found in all cells Cell Theory Comprehension Check: Answers 1. All living things have the same functional unit. Statement 1: All living things are made of cells 2. Cell division produces more cells of the same kind. Statement 3: New cells come from pre-exiting ones 3. The DNA in a daughter cell will be the same as that found in the parent cell Statement 4: Hereditary information is passed from parent to daughter cell 4. Cells have metabolic processes. Statement 6: Energy flow occurs between cells 5. The four main macromolecules are found in all cells Statement 5: All cells have similar chemical composition. Cell Theory The Discovery of Cells The invention of the microscope was responsible for the eventual discovery of the cell and the formulation of the Cell Theory. The first breakthrough came from Robert Hooke in 1665 who made a compound microscope and used it to Hooke’s observe and draw pieces of cork. microscope Cell Theory The Discovery of Cells Hooke saw symmetrical borders in what appeared to be tiny holes in the cork he referred to these as cells. What Hooke actually saw without realizing were the empty cell walls of plant cells. He coined the name cell from the Latin word ‘cella’ which is a small room where monks live. (Top image) Robert Hooke's detailed drawing showing the cell walls of plant cells. (Bottom image) Hooke's compound microscope. Cell Theory The Discovery of Cells Hooke recorded many of these observations in his famous publication, micrographia. Left image: Hooke’s drawing of a flea Right image: An engraving of a louse Cell Theory Comprehension Check… Summarise Robert Hooke’s contribution to cell theory including: What he observed How he observed it The significance of his observation. Cell Theory Comprehension Check: Answer Robert Hooke built a microscope which he then used to observe pieces of cork. This allowed him to see the empty cell walls of the cork , showing that cells had partitions between them. This was the first time that these structures were given the name cella or cells. Cell Theory Antonie van Leeuwenhoek Observed the same minute structures as Hooke, and further explored cells and observed mobile objects. This discovery led him to believe that these were living organisms since movement is a characteristic of life. Cell Theory Antonie van Leeuwenhoek Leuwenhoek called these tiny creatures “animalcules,” These organisms were actually bacteria and protozoa. The image to the right shows Leeuwenhoek’s detailed animalcule drawings Cell Theory Antonie van Leeuwenhoek Leeuwenhoek made many other discoveries such as identifying red blood cells and bacteria. He was the first to observe fertilization and report that it required the sperm cell to enter the egg cell. This would be the key to disproving the theory of spontaneous generation. This was the theory that living things could arise from non-living objects. Cell Theory Comprehension Check… Summarise Leeuwenhoek's contribution to cell theory including: What he observed How he observed it The significance of his observation. Cell Theory Comprehension Check: Answers Leeuwenhoek observed tiny moving objects which he named Animalcules. He achieved this by grinding and polishing his own custom lenses which allowed him to observe objects which had never been seen before. He came to the conclusion that all iving things move. Cell Theory Henri Dutrochet Approximately one hundred years later, Henri Dutrochet claimed that cell was the fundamental element of life. This also made it clear that the cell is also a physiological unit as well as a structural unit. In 1804, JHF Link and Karl Rudolphi further contributed to the nature of cells, proving that cells have independent cell walls. Cell Theory The History of Cell Theory The cell theory came about much later than the initial discovery of cells, having been first suggested by the German scientists Matthias Schleiden and Theodor Schwann in 1838 and 1839. Left: Theodor Schwann Right: Matthias Schleiden Cell Theory The History of Cell Theory - Schleiden Schleiden undertook microscopic research on plants and was the first to describe their cellular structure including the presence of the plant cell nucleus. Cell Theory The History of Cell Theory - Schwann Schwann built on Schleiden’s work and in 1839 described the cellular structure of animal cells. Having previously studied a range of animal tissues including nerves, muscles and blood vessels, Schwann was able to observe and record the different properties of the cells in these structures. Animal cell structure Cell Theory The History of Cell Theory - Schwann Schwann eventually published his work on cells which drew three main conclusions regarding cell theory. These were: 1. The cell is the fundamental structure of life, 2. All organisms are made up of cells, and 3. Cells are formed through spontaneous generation. While the first two conclusion are true, are a part of the basic theory which underpins cell biology today, the concept of spontaneous generation was later disproved and rejected. Cell Theory The History of Cell Theory – Rudulph Virchow Rudolph Virchow, after years of studying cell reproduction, eventually concluded that cells arise only from pre-existing cells. Cell Theory The History of Cell Theory – Rudulph Virchow With the evolution of modern molecular biology, the theory of cells has been expanded to cover concepts of heredity, cell energy production, and the study of the different structural components of cells. Virchow’s drawings of cell theory are pictured right. He went on to discover the origin of cancers including leukemia in 1847. Cell Theory Comprehension Check… For each of the following statements, name the scientist who made the discovery. 1. Concluded that all cells came from pre-existing ones. 2. All organisms are made up of cells 3. Living objects are able to move 4. Plant cells have a nucleus Cell Theory Comprehension Check: Answers For each of the following statements, name the scientist who made the discovery. 1. Concluded that all cells came from pre-existing ones. Virchow 2. All organisms are made up of cells Schwann 3. Living objects are able to move Leeuwenhoek 4. Plant cells have a nucleus Schleiden